Manar Hamzah Herez Al-zerajawi

This research proposes a reliability-based methodology to optimize maintenance planning for flexible pavements by employing nonlinear deterioration modelling. The study focuses on Al-Najaf, Iraq, where pavement infrastructure faces compounded stresses due to high temperatures and substantial traffic volumes. Traditional linear models are insufficient for capturing the real-time progression of pavement degradation in such environments, resulting in suboptimal maintenance interventions. To address this gap, the study calibrates two nonlinear models—the Weibull and exponential functions, using performance data gathered between 2016 and 2024 across three representative road corridors. The Weibull model outperformed its counterpart, with a coefficient of determination (R²) of 0.946, as well as lower Root Mean Square Error (RMSE) and Akaike Information Criterion (AIC) values, indicating better predictive capacity. Reliability analysis was integrated into the modelling process to estimate the probability of pavement failure over time, aiding in the determination of optimal intervention points. Five maintenance strategies were evaluated: preventive, conditionbased, hybrid, risk-based, and no-maintenance. Among these, the hybrid strategy emerged as the most efficient in terms of lifecycle cost-effectiveness and service life extension, achieving a pavement lifespan of 12.5 years while maintaining a balanced overall cost. An economic evaluation using Net Present Value (NPV) and Monte Carlo simulation highlighted the system’s sensitivity to environmental and operational variables, including increased axle loads and temperature fluctuations. The study concludes with policy-oriented recommendations, advocating for the integration of nonlinear and reliability models into national Pavement Management Systems (PMSs), and proposing the pilot implementation of hybrid strategies in cities with similar climatic and loading conditions.

Warm Mix Asphalt (WMA) technology is recently grabbing the worldwide attention due to reduce the heat required to decrease the viscosity of bitumen and increase the workability of asphalt mixtures. This technology also reduces the temperature of mixing and paving process comparing to the temperature required for the traditional hot mix asphalt, as well as increase the haul span distance. Reducing the mixing and laying temperatures leads to several benefits including: less green house gas emissions, energy savings cost, and longer construction season. Despite the promising benefits of this technology, there are some concerns regarding the durability and long-term performance. Much research and development have been carried out around the world into warm-mix technology. These approach have the same basic goal but in differing ways. To date, HMA is commonly used in road construction in Iraq, while the use of WMA is totally new. Accordingly, there is a persistent need to study the potential application of WMA to manufacture a more eco-friendly products. However, before carrying out testing works, a desktop survey should be completed to explore the wide variety of WMA's available to attempt to narrow down the possible products of WMA that could be applicable with reference to Iraq's climate. Iraq has a hot and dry climate differs from most of the countries where this technology has been originally developed. This paper investigates the potential use of this technology in the context of Iraq.

Road pavements are pivotal to the infrastructure, transportation and ultimate efficiency of both the public and the economy. However, they are undeniably having detrimental effects on an already compromised environment. Consequently, a re-think about road pavement construction materials is of paramount importance. Cold mix asphalt (CMA) is a low carbon manufacturing approach to the production of flexible pavement material that has proved to be very promising, both economically and ecologically. This technology allows the manufacture of mixtures at ambient temperatures without heating huge amounts of aggregates and bitumen, this decreasing CO2 emissions and saving energy. In spite of these positive impacts, CMA has a high sensitivity to traffic and environmental stresses due to the existence of water within the mixture, this of major concern to the industry. This study aims to review types of CMA and the main developments involved in cold bitumen emulsion mixture (CBEM) technology that can be used without decreasing in-service performance. This review also aims to provide a practical guide for the manufacture of bitumen emulsion and the design procedure of CBEM for the road pavements industry. Finally, it can be suggested that CMA is a crucial technique for pavement construction, as it provides acceptable performance alongside energy-saving and ecological objectives.

In recent years, global climate change and energy shortages have become serious issues of common concern internationally. The majority of roads and highways are paved using hot mix asphalt (HMA) technology. The manufacture of hot mix asphalt is a key source of energy consumption, greenhouse gas emissions and air pollution. As such, efforts have been made to develop sustainable techniques to reduce energy consumption by lowering manufacturing temperatures, which in turn, will reduce CO2 emissions and subsequent negative impacts on the environment. Cold bitumen emulsion mixtures (CBEMs) are an excellent alternative to traditional HMA, from both an economic and environmental point of views. However, there are certain issues related to the mechanical properties of CBEMs that make them inferior to HMA, limiting their use to low traffic roads, reinstatement works and footways. Accordingly, the development of a CBEM with high early strength and minimal curing time is of increasing interest to researchers in the asphalt industry. The aim of this research work was to develop a new, high performance and environmentally friendly, surface course, cold bitumen emulsion mixture for heavily trafficked roads. This aim has been achieved by i) addressing the longstanding problems associated with conventional bitumen emulsions, namely large and non-uniform distribution of bitumen droplets within the emulsion, and ii) reducing the long curing time of CBEMs by replacing conventional limestone filler (LF) with a new secondary cementitious filler made primarily from waste materials. Ultrasound technology was used to reduce the size of the bitumen droplets through the cavitation phenomenon. A cationic bitumen emulsion (C50B4) was treated using ultrasound apparatus, over different periods of time. The results revealed an 85% reduction in mean droplet size (D50), under 7 minutes sonication treatment compared to the untreated sample. Reductions in D90 and D10 were 90% and 86%, respectively, in comparison to the untreated sample. The particle size distribution (PSD) curve shows more uniformly distributed droplets closer to the mean values, in comparison to the untreated emulsion. The viscosity of the 7minute sonicated bitumen emulsion decreased by 28%, compared to the untreated emulsion. CBEM-LF, made with 7-minute sonicated bitumen emulsion, showed an enhancement in indirect tensile stiffness modulus (ITSM) at 3 days curing by approximately 70%, compared with the same mixture containing conventional bitumen emulsion. To eliminate the long curing time required by CBEMs, a new cementitious filler was developed from waste materials and used as a substitute to conventional LF. The new alkali ternary blended filler, ATBF2, comprises ordinary Portland cement (OPC), a high volume of waste sewage sludge fly ash (SSFA) and calcium carbide residue (CCR). A waste calcium hydroxide solution was used as a replacement for the aggregate pre-wetting water in the CBEM. CCR played a vital role activating the SSFA by breaking the glassy phases of the non-amorphous silica in the SSFA, while the waste calcium hydroxide solution increased the hydraulic reactivity of the cementitious components. Scanning electron microscopy (SEM) and x-ray diffraction (XRD) were used to investigate the development of hydration products in the new CBEM. Concentrations of heavy metals in the samples incorporating ATBF2, were observed to be less than the regulatory levels determined for hazardous materials. The mechanical properties of the novel CBEM incorporating both the sonicated bitumen emulsion and ATBF2 filler, were investigated in terms of ITSM at different curing times, rutting resistance, fatigue resistance, water damage resistance and age hardening. The said mixture offers a substantial improvement in stiffness modulus, compared to HMA and CBEM containing conventional emulsion and LF. The ITSM for the newly developed CBEM at 3 days of age, increased by approximately 19 times that of the conventional cold mixture, and almost 2.5 times that of traditional 100/150 HMA. The new mixture also displayed considerably higher resistance to permanent deformation in comparison to the reference cold and hot asphalt mixtures, demonstrating its potential for use in heavily trafficked roads. Resistance to fatigue was significantly enhanced by the use of both ATBF2 and the modified emulsion in the CBEM, compared to conventional cold and hot mixtures. This mixture is more durable because of improvements in resistance to water damage and enhanced long term ageing performance. This improvement has been achieved by the presence of smaller bitumen droplets that provide more bitumen surface area and even coating of aggregate particles. This helps form a cohesive mixture working in parallel with the hydration products which resulted from the hydration process of the cementitious filler in the presence of water within the bitumen-water solution.

In this study, the effect of a novel technology for producing high quality cold mix asphalt using modified bitumen emulsion has been investigated in terms of indirect tensile stiffness modulus. Cold mix asphalt produced using conventional emulsion and limestone filler has three main disadvantages, namely low early strength due to high amount of water with in the mix, long curing time ranging from 2-24 months and high air voids content. The new bitumen emulsion produced in this study has low viscosity compared with the emulsion from which it has been produced. The results reported contains a comparison between the viscosity of the emulsions, and the indirect tensile stiffness modulus of a control conventional cold mix asphalt and the new high quality cold mix asphalt with low viscosity. Interestingly the reduction of the 28% in the viscosity of the new emulsion causes an improvement of the indirect tensile stiffness modulus reached 216%, which indicate the outstanding achievement.

Cold bituminous emulsion mixture (CBEM) is a sustainable alternative to the conventional hot mix asphalt (HMA) due to the environmental and safety issues associated with the use of the latter. However, CBEM experiences some drawbacks including low early life strength, high air voids and long curing time, thus it needs from 2-24 months to reach its ultimate strength. Accordingly, the applications for CBEMs have been limited to low/medium trafficked roads, footways and reinstatements. The aim of this study is to develop a new secondary cementitious material incorporating a high volume of sewage sludge fly ash (SSFA) with low ordinary Portland cement (OPC) content and carbide lime waste (CLW), to be used as a replacement to the conventional limestone filler in CBEM. The results demonstrated a significant improvement in the performance of the developed CBEM in terms of indirect tensile stiffness modulus (ITSM) and microstructure analysis compared to the conventional CBEM incorporating limestone filler. Furthermore, the developed mixture has being comparable to the mixtures including OPC and the conventional HMA. Scanning electron microscopy (SEM) analysis revealed that a considerable changes in the microstructure components over the curing ages has been developed which confirm the creation of cementitious products such as C-S-H and ettringite.